Early lettered Utah state highway corridors

[US 89]

So I did a little digging on the early history of the Utah state highway system. Although state highways began in 1910, apparently enough roads were added over the next decade that the state legislature worried that the system was getting too big. So in 1919, they restricted the state highway system to a series of defined, lettered corridors, plus any other roads that had been improved by the state as federal-aid projects.

I made a couple of maps in the very professional MacOS Preview of what that lettered system looked like, both in 1919 and after six years of additions:



To my knowledge, none of these letters were ever signed. The most important of those roads were given signed "state trunk line" numbers that were probably signed in the mid 1920s. In 1927, the legislature scrapped the lettered corridors entirely and started assigning individual route numbers, which continued the state trunk line numbers with one exception (17 became 41).

It's really fascinating looking at this map and comparing to what ultimately developed. A lot of the modern interstates and US highway corridors are recognizable... but many are not. Conversely, some of the corridors here aren't state highways anymore, like M and R...and some aren't even roads! Good luck driving E (the Lincoln Highway) across the state now - most of it in Tooele County is now within the Dugway Proving Ground's boundaries.

[Scott5114]

Why isn't there a P?

[US 89]

Why isn't there a P?

There is no P on the map because that was the umbrella designation covering any federal-aid project state roads that weren't on any of the other corridors - of which there were many scattered across the state. That isn't to say that there weren't federal aid projects along the explicitly listed letter corridors, because there absolutely were, but in the minds of the 1919 legislature trying to save money and slim down the state highway system, a federal aid project was the only way to get yourself a state highway that wasn't on one of their defined corridors that they thought were important enough to be state roads no matter what. The original 1919 system assigned only through O, so P made sense to be the "leftovers" designation.

This worked briefly, but after a few years the legislature started adding connectors to federal-aid roads that weren't federal-aid roads themselves. R and S fell into that category - S in particular was not even 3 miles long. That seems like a very quick way to run through the alphabet, which I'm guessing is why they switched to legislative numbering in 1927 to match what was starting to be posted in the field by then.

ETA: here's a version of those maps with the federal aid roads that had been built by that time in tan.

[andy3175]

Wow, I never knew this existed. Is there a written description of each lettered corridor?

Regards,
Andy

[US 89]

Wow, I never knew this existed. Is there a written description of each lettered corridor?

Regards,
Andy

This is all sourced from a Wikipedia project page, which itself was sourced (mostly by NE2) from a bunch of early state laws and state road commission reports. A lot of the links may not work anymore, but all the info is there.

I'm also realizing the second round of maps I made doesn't include any of the National Forest road corridors, which went in the same category as those federal-aid projects. Oh well, I'll update those when I find the time...